Student Loan Payoff Calculator with Extra Payments
Use the full debt payoff planner to compare snowball, avalanche, and hybrid plans side by side.
Calculate your payoff
What-if: extra payments and lump sums
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Disclaimer
Not financial advice. This calculator is for educational purposes only and is not financial advice, tax advice, or a recommendation. Consider speaking with a qualified professional about your situation.
Assumptions. Interest is calculated monthly as balance × APR ÷ 12 and applied before each payment (monthly compounding). If you leave a minimum payment blank, it is estimated as the largest of: 2% of the balance, one month's interest + 1% of the balance, or $25 — actual minimums vary by lender. Simulations stop at 600 months. Displayed amounts are rounded to the nearest cent.
Data sources. Formulas: standard amortization math. No external data feeds. Page last updated: 2026-10-18.
How the math works
Student debt usually arrives as several loans with different balances and rates, which fits the multi-debt engine directly: enter each loan's balance, APR, and minimum, and the preset here is avalanche, so leftover budget after minimums goes to the highest-rate loan first. The extra-payment field is the center of this page — add a fixed extra amount to any loan and the schedule, payoff date, and total interest update. Because the engine re-sorts every month, the extra keeps flowing to whichever unpaid loan currently carries the highest APR.
Federal student loans offer several repayment plans — standard, graduated, and income-driven options among them. This calculator models standard amortization math only: fixed monthly payments against interest that compounds monthly at APR ÷ 12. It does not compute income-driven payment amounts and does not model forgiveness provisions or deferment. For a variable-rate private loan, enter the current rate; the simulation holds it constant, so the results describe the current rate extended across the payoff period.
Four assumptions apply to every run. One, monthly compounding: interest accrues once per month at balance × APR ÷ 12, before payments. Two, a blank minimum is estimated as the largest of 2% of the balance, one month's interest plus 1% of the balance, or $25; servicer minimums are set differently, so the figure on the statement is the more faithful input. Three, the simulation stops at 600 months, and a plan that has not cleared every balance by then is reported as not paid off within the simulation limit. Four, all math runs in full double precision with no per-month rounding; displayed dollars are rounded half-up to the nearest cent, with totals summed from unrounded values before rounding.
A one-time payment such as a tax refund can be tested on the lump-sum calculator, and the debt-free date calculator presents the same math with the calendar month as the headline.
Worked example
Two loans, $600 monthly budget plus $100 extra each month on the federal loan, avalanche ordering, starting November 2026. Federal Direct Loan: $12,000 at 6.53% APR, $150 minimum. Private Refi Loan: $8,000 at 4.99% APR, $120 minimum.
| Month | Interest | Payment | Federal Direct end balance | Private Refi end balance |
|---|---|---|---|---|
| December 2026 | $98.57 | $700.00 | $11,485.30 | $7,913.27 |
Month 1 in detail: $65.30 of interest on the federal loan and $33.27 on the private loan is added first ($98.57 displayed after rounding); $150 and $120 minimums are paid; the $100 extra and the remaining $330 of budget both target the federal loan as the highest-APR debt. The full run: 33 payments, debt-free August 2029, $1,553.55 total interest, $21,553.55 total paid.
Frequently asked questions
Does this calculator model income-driven repayment plans?
No. Federal student loans offer several repayment plans, including standard, graduated, and income-driven options. This calculator models standard amortization math only: fixed monthly payments against interest compounding monthly at APR ÷ 12. It does not compute income-driven payment amounts or model forgiveness provisions.
How do extra payments change the results?
A per-loan extra amount is applied every month after minimums, flowing to the highest-APR unpaid loan under the avalanche preset. In the worked example, $100 extra per month on the federal loan produces a 33-month payoff ending August 2029 with $1,553.55 of total interest. Removing the extra re-runs the same inputs without it.
Which loan receives the extra payment first?
Under the avalanche preset, leftover budget and extras go to the unpaid loan with the highest APR. The ordering is recomputed every month from current balances, so if rates or balances change the target, the money follows. With a single loan, or when only one remains, all extra money goes to it.
What APR should I enter for a variable-rate loan?
Enter the current rate. The simulation holds whatever APR you type constant for the entire run, so the results describe the current rate extended over the payoff period. If the rate later changes, re-running with the new rate gives the updated figures. The methodology notes this as a limitation.
Why are displayed totals rounded to the nearest cent?
All internal math runs in full double precision with no per-month rounding; totals are summed from unrounded values and then rounded half-up to cents for display. Each schedule row is rounded independently, so adding displayed rows can differ from the displayed total by a cent.
Can I include debts other than student loans here?
The inputs are generic — balance, APR, minimum — so any installment or revolving debt can be entered. The math does not distinguish loan types. The page's framing and the federal-plan note are student-loan specific, but the engine treats every row the same way.